Residential Solutions HVAC Monitoring and Diagnosis

ABSTRACT

A monitoring system for a heating, ventilation, and air conditioning (HVAC) system of a residence includes a monitoring device installed at the residence and a server located remotely from the residence. The monitoring device measures an aggregate current supplied to a plurality of components of the HVAC system and transmits current data based on the measured aggregate current. The server receives the transmitted current data and, based on the received current, assesses whether a failure has occurred in a first component of the plurality of components of the HVAC system and assesses whether a failure has occurred in a second component of the plurality of components of the HVAC system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/447,681 filed on Feb. 28, 2011 and U.S. Provisional Application No.61/548,009 filed on Oct. 17, 2011. The disclosures of the aboveapplications are incorporated herein by reference in their entirety.

FIELD

The present disclosure relates to environmental comfort systems and moreparticularly to remote monitoring and diagnosis of residentialenvironmental comfort systems.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

A residential HVAC (heating, ventilation, and air conditioning) systemcontrols environmental parameters, such as temperature and humidity, ofa residence. The HVAC system may include, but is not limited to,components that provide heating, cooling, humidification, anddehumidification. The target values for the environmental parameters,such as a temperature set point, may be specified by a homeowner.

Referring now to FIG. 1, a block diagram of an example HVAC system ispresented. In this particular example, a forced air system with a gasfurnace is shown. Return air is pulled from the residence through afilter 110 by a blower 114. The blower 114, also referred to as a fan,is controlled by a control module 118. The control module 118 receivessignals from a thermostat 122. For example only, the thermostat 122 mayinclude one or more temperature set points specified by the homeowner.

The thermostat 122 may direct that the blower 114 be turned on at alltimes or only when a heat request or cool request is present. The blower114 may also be turned on at a scheduled time or on demand. In variousimplementations, the blower 114 can operate at multiple speeds or at anyspeed within a predetermined range. One or more switching relays (notshown) may be used to control the blower 114 and/or to select a speed ofthe blower 114.

The thermostat 122 also provides the heat and/or cool requests to thecontrol module 118. When a heat request is made, the control module 118causes a burner 126 to ignite. Heat from combustion is introduced to thereturn air provided by the blower 114 in a heat exchanger 130. Theheated air is supplied to the residence and is referred to as supplyair.

The burner 126 may include a pilot light, which is a small constantflame for igniting the primary flame in the burner 126. Alternatively,an intermittent pilot may be used in which a small flame is first litprior to igniting the primary flame in the burner 126. A sparker may beused for an intermittent pilot implementation or for direct burnerignition. Another ignition option includes a hot surface igniter, whichheats a surface to a high enough temperature that when gas isintroduced, the heated surface causes combustion to begin. Fuel forcombustion, such as natural gas, may be provided by a gas valve (notshown).

The products of combustion are exhausted outside of the residence, andan inducer blower 134 may be turned on prior to ignition of the burner126. The inducer blower 134 provides a draft to remove the products ofcombustion from the burner 126. The inducer blower 134 may remainrunning while the burner 126 is operating. In addition, the inducerblower 134 may continue running for a set period of time after theburner 126 turns off. In a high efficiency furnace, the products ofcombustion may not be hot enough to have sufficient buoyancy to exhaustvia conduction. Therefore, the inducer blower 134 creates a draft toexhaust the products of combustion.

A single enclosure, which will be referred to as an air handler 208, mayinclude the filter 110, the blower 114, the control module 118, theburner 126, the heat exchanger 130, the inducer blower 134, theexpansion valve 188, the evaporator 192, and the condensate pan 196.

In the HVAC system of FIG. 1, a split air conditioning system is alsoshown. Refrigerant is circulated through a compressor 180, a condenser184, an expansion valve 188, and an evaporator 192. The evaporator 192is placed in series with the supply air so that when cooling is desired,the evaporator removes heat from the supply air, thereby cooling thesupply air. During cooling, the evaporator 192 is cold, which causeswater vapor to condense. This water vapor is collected in a condensatepan 196, which drains or is pumped out.

A compressor control module 200 receives a cool request from the controlmodule 118 and controls the compressor 180 accordingly. The compressorcontrol module 200 also controls a condenser fan 204, which increasesheat exchange between the condenser 184 and outside air. In such a splitsystem, the compressor 180, the condenser 184, the compressor controlmodule 200, and the condenser fan 204 are located outside of theresidence, often in a single outdoor enclosure 212.

In various implementations, the compressor control module 200 may simplyinclude a run capacitor, a start capacitor, and a contactor or relay. Infact, in certain implementations, the start capacitor may be omitted,such as when a scroll compressor instead of a reciprocating compressoris being used. The compressor 180 may be a variable capacity compressorand may respond to a multiple-level cool request. For example, the coolrequest may indicate a mid-capacity call for cool or a high capacitycall for cool.

The electrical lines provided to the outdoor enclosure 212 may include a240 volt mains power line and a 24 volt switched control line. The 24volt control line may correspond to the cool request shown in FIG. 1.The 24 volt control line controls operation of the contactor. When thecontrol line indicates that the compressor should be on, the contactorcontacts close, connecting the 240 volt power supply to the compressor.In addition, the contactor may connect the 240 volt power supply to acondenser fan 204. In various implementations, such as when the outdoorenclosure 212 is located in the ground as part of a geothermal system,the condenser fan 204 may be omitted. When the 240 volt mains powersupply arrives in two legs, as is common in the U.S., the contactor mayhave two sets of contacts, and is referred to as a double-polesingle-throw switch.

Monitoring of operation of components in the outdoor enclosure 212 andthe air handler 208 has traditionally been performed by multiplediscrete sensors, measuring current individually to each component. Forexample, a sensor may sense the current drawn by a motor, another sensormeasures resistance or current flow of an igniter, and yet anothersensor monitors a state of a gas valve. However, the cost of thesesensors and the time required for installation has made monitoring costprohibitive.

SUMMARY

A monitoring system for a heating, ventilation, and air conditioning(HVAC) system of a residence includes a monitoring device installed atthe residence and a server located remotely from the residence. Themonitoring device measures an aggregate current supplied to a pluralityof components of the HVAC system and transmits current data based on themeasured aggregate current. The server receives the transmitted currentdata and, based on the received current, assesses whether a failure hasoccurred in a first component of the plurality of components of the HVACsystem and assesses whether a failure has occurred in a second componentof the plurality of components of the HVAC system.

In other features, the monitoring device samples the aggregate currentover a time period, performs a frequency domain analysis on the samplesover the time period, and transmits frequency domain data to the server.The server identifies transition points in the current data and analyzesthe frequency domain data around the identified transition points. Theserver determines whether the failure has occurred in the firstcomponent by comparing the frequency domain data to baseline data. Theserver adapts the baseline data based on normal operation of the HVACsystem. The monitoring device determines a single current value for thetime period and transmits the single current value to the server withouttransmitting the samples to the server.

In further features, the single current value is one of a root meansquared current, an average current, and a peak current. The monitoringdevice measures the aggregate current over a series of consecutive timeperiods and transmits a frame of information to the server for each ofthe time periods. For a first period of the time periods, the monitoringdevice transmits a first frame including (i) a single value of theaggregate current during the first period and (ii) a frequency domainrepresentation of the aggregate current during the first period.

In still other features, the first frame does not include individualsamples of the aggregate current. The first frame includes a voltagemeasurement of power arriving at the HVAC system, a temperaturemeasurement, and a representation of status of HVAC control lines duringthe first period. The monitoring device records control signals from athermostat and transmits information based on the control signals to theserver. The control signals include at least one of call for heat, callfor fan, and call for cool.

In other features, the monitoring device is located in close proximityto an air handler unit of the HVAC system. A second monitoring device islocated in close proximity to a second enclosure of the HVAC system,wherein the second enclosure includes at least one of a compressor and aheat pump heat exchanger. The second monitoring device (i) measures anaggregate current supplied to a plurality of components of the secondenclosure and (ii) transmits current data based on the measuredaggregate current to the server. The second monitoring device transmitsthe current data to the server via the monitoring device.

In further features, the monitoring device includes a switch thatselectively interrupts an enabling signal to a compressor of the HVACsystem. The monitoring device interrupts the enabling signal in responseto at least one of (i) a value from a water sensor, (ii) a locked rotorcondition of the compressor, and (iii) a command from the server. Theserver (i) generates an alert in response to determining presence of afault of either the first component or the second component and (ii)sends the alert to at least one of a homeowner of the residence and aninstallation contractor.

In still other features, the server (i) selectively predicts an impedingfailure of the first component based on the received current data, (ii)selectively predicts an impeding failure of the second component basedon the received current data, and (iii) generates an alert in responseto prediction of impending failure. The plurality of components of theHVAC system includes at least two components selected from: a flamesensor, a solenoid-operated gas valve, a hot surface igniter, acirculator blower motor, an inducer blower motor, a compressor, apressure switch, a capacitor, an air filter, a condensing coil, anevaporating coil, and a contactor.

A method of monitoring a heating, ventilation, and air conditioning(HVAC) system of a residence includes using a monitoring deviceinstalled at the residence, measuring an aggregate current supplied to aplurality of components of the HVAC system, and transmitting currentdata based on the measured aggregate current to a server locatedremotely from the residence. The method includes receiving thetransmitted current data at the server and based on the receivedcurrent, assessing whether a failure has occurred in a first componentof the plurality of components of the HVAC system. The method furtherincludes, based on the received current, assessing whether a failure hasoccurred in a second component of the plurality of components of theHVAC system.

In other features, the method includes sampling the aggregate currentover a time period, performing a frequency domain analysis on thesamples over the time period, and transmitting frequency domain data tothe server. The method includes identifying transition points in thecurrent data, and analyzing the frequency domain data around theidentified transition points. The method further includes determiningwhether the failure has occurred in the first component by comparing thefrequency domain data to baseline data, and adapting the baseline databased on normal operation of the HVAC system.

In still other features, the method includes determining a singlecurrent value for the time period and transmitting the single currentvalue to the server without transmitting the samples to the server. Thesingle current value is one of a root mean squared current, an averagecurrent, and a peak current. The method includes measuring the aggregatecurrent over a series of consecutive time periods, and transmitting aframe of information to the server for each of the time periods.

In still further features, the method includes, for a first period ofthe time periods, transmitting a first frame including (i) a singlevalue of the aggregate current during the first period and (ii) afrequency domain representation of the aggregate current during thefirst period. The first frame does not include individual samples of theaggregate current. The first frame includes a voltage measurement ofpower arriving at the HVAC system, a temperature measurement, and arepresentation of status of HVAC control lines during the first period.

In other features, the method includes recording control signals from athermostat, and transmitting information based on the control signals tothe server. The control signals include at least one of call for heat,call for fan, and call for cool. The monitoring device is located inclose proximity to an air handler unit of the HVAC system, and themethod further includes measuring an aggregate current supplied to aplurality of components of a second enclosure of the HVAC system. Thesecond enclosure includes at least one of a compressor and a heat pumpheat exchanger, and the method includes transmitting current data basedon the measured aggregate current to the server.

In still other features, the method includes transmitting the currentdata from the second monitoring device to the server via the monitoringdevice, and communicating with the monitoring device using power linecommunication. The method includes selectively interrupting an enablingsignal to a compressor of the HVAC system in response to at least one of(i) a value from a water sensor, (ii) a locked rotor condition of thecompressor, and (iii) a command from the server. The method includessending an alert in response to determining presence of a fault ofeither the first component or the second component, wherein the alert issent to at least one of a homeowner of the residence and an installationcontractor.

In further features, the method includes selectively predicting animpeding failure of the first component based on the received currentdata, selectively predicting an impeding failure of the second componentbased on the received current data, and generating an alert in responseto prediction of impending failure. The plurality of components of theHVAC system includes at least two components selected from: a flamesensor, a solenoid-operated gas valve, a hot surface igniter, acirculator blower motor, an inducer blower motor, a compressor, apressure switch, a capacitor, an air filter, a condensing coil, anevaporating coil, and a contactor. The method includes transmitting thecurrent data to a gateway wirelessly, wherein the gateway forwards thecurrent data to the server over the Internet.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a block diagram of an example HVAC system according to theprior art;

FIG. 2 is a functional block diagram of an example system showing anHVAC system of a single residence;

FIGS. 3A-3C are functional block diagrams of control signal interactionwith the air handler monitor module;

FIG. 4A is a functional block diagram of an example implementation ofthe air handler monitor module;

FIG. 4B is a functional block diagram of an example implementation ofthe compressor monitor module;

FIGS. 5A-5I are block diagrams of example implementations of the airhandler monitor module;

FIG. 5J is a data flow diagram of a monitor module according to theprinciples of the present disclosure;

FIG. 6 is a flowchart depicting a brief overview of an example moduleinstallation in a retrofit application;

FIG. 7 is a flowchart of example operation in capturing frames of data;

FIG. 8 is an example functional schematic of example HVAC components;

FIG. 9 is an example time domain trace of aggregate current for abeginning of a heat cycle;

FIGS. 10A-10C are example time domain representations of aggregatecurrent related to the hot surface igniter;

FIGS. 11A-11B show example frequency content corresponding to FIGS. 10Aand 10C, respectively;

FIG. 11C shows a frequency domain comparison of FIGS. 11A and 11B;

FIGS. 12A-12B are example time domain plots depicting asolenoid-operated gas valve functioning and failing to function,respectively;

FIG. 12C is a frequency domain comparison of FIGS. 12A and 12B;

FIGS. 13A-13B are time domain traces of current and voltage of a motor;

FIG. 13C is a time domain subtraction of FIGS. 13A and 13B;

FIGS. 14A-14B are frequency domain analyses of FIG. 13A and 13B,respectively;

FIG. 14C is a frequency domain comparison of FIGS. 14A and 14B;

FIGS. 15A-15G depict example implementation of cloud processing ofcaptured data; and

FIGS. 16A and 16B present example failures and features for indoor andoutdoor units, respectively, that can be detected and/or predicted inaddition to example data used in various implementations to perform thedetection and/or prediction.

DETAILED DESCRIPTION

According to the present disclosure, sensing/monitoring modules can beintegrated with a residential HVAC (heating, ventilation, and airconditioning) system. As used in this application, the term HVACencompasses all environmental comfort systems in a home or business,including heating, cooling, humidifying, and dehumidifying, and coversdevices such as furnaces, heat pumps, humidifiers, dehumidifiers, andair conditioners. The term HVAC is a broad term, in that an HVAC systemaccording to this application does not necessarily include both heatingand air conditioning, and may instead have only one or the other.

In split HVAC systems with an air handler unit (often, indoors) and acompressor unit (often, outdoors), an air handler monitor module and acompressor monitor module, respectively, can be used. The air handlermonitor module and the compressor monitor module may be integrated bythe manufacturer of the HVAC system, may be added at the time of theinstallation of the HVAC system, and/or may be retrofitted to anexisting system.

The air handler monitor and compressor monitor modules monitor operatingparameters of associated components of the HVAC system. For example, theoperating parameters may include power supply current, power supplyvoltage, operating and ambient temperatures, fault signals, and controlsignals. The air handler monitor and compressor monitor modules maycommunicate data between each other, while one or both of the airhandler monitor and compressor monitor modules uploads data to a remotelocation. The remote location may be accessible via any suitablenetwork, including the Internet.

The remote location includes one or more computers, which will bereferred to as servers. The servers execute a monitoring system onbehalf of a monitoring company. The monitoring system receives andprocesses the data from the air handler monitor and compressor monitormodules of homeowners who have such systems installed. The monitoringsystem can provide performance information, diagnostic alerts, and errormessages to a homeowner and/or third parties, such as a designated HVACcontractor.

The air handler monitor and compressor monitor modules may each sense anaggregate current for the respective unit without measuring individualcurrents of individual components. The aggregate current data may beprocessed using frequency domain analysis, statistical analysis, andstate machine analysis to determine operation of individual componentsbased on the aggregate current data. This processing may happenpartially or entirely in a server environment, outside of thehomeowner's residence.

Based on measurements from the air handler monitor and compressormonitor modules, the monitoring company can determine whether HVACcomponents are operating at their peak performance and can advise thehomeowner and the contractor when performance is reduced. Thisperformance reduction may be measured for the system as a whole, such asin terms of efficiency, and/or may be monitored for one or moreindividual components.

In addition, the monitoring system may detect and/or predict failures ofone or more components of the system. When a failure is detected, thehomeowner can be notified and potential remediation steps can be takenimmediately. For example, components of the HVAC system may be shut downto minimize damage or HVAC components and/or prevent water damage. Thecontractor can also be notified that a service call will be required.Depending on the contractual relationship between the homeowner and thecontractor, the contractor may immediately schedule a service call tothe residence.

The monitoring system may provide specific information to thecontractor, including identifying information of the homeowner's HVACsystem, including make and model numbers, as well as indications of thespecific part numbers that appear to be failing. Based on thisinformation, the contractor can allocate the correct repair personnelthat have experience with the specific HVAC system and/or component. Inaddition, the service technician is able to bring replacement parts,avoiding return trips after diagnosis.

Depending on the severity of the failure, the homeowner and/orcontractor may be advised of relevant factors in determining whether torepair the HVAC system or replace some or all of the components of theHVAC system. For example only, these factors may include relative costsof repair versus replacement, and may include quantitative orqualitative information about advantages of replacement equipment. Forexample, expected increases in efficiency and/or comfort with newequipment may be provided. Based on historical usage data and/orelectricity or other commodity prices, the comparison may also estimateannual savings resulting from the efficiency improvement.

As mentioned above, the monitoring system may also predict impendingfailures. This allows for preventative maintenance and repair prior toan actual failure. Alerts regarding detected or impending failuresreduce the time when the HVAC system is out of operation and allows formore flexible scheduling for both the homeowner and contractor. If thehomeowner is out of town, these alerts may prevent damage from occurringwhen the homeowner is not present to detect the failure of the HVACsystem. For example, failure of heat in winter may lead to pipesfreezing and bursting.

Alerts regarding potential or impending failures may specify statisticaltimeframes before the failure is expected. For example only, if a sensoris intermittently providing bad data, the monitoring system may specifyan expected amount of time before it is likely that the sensoreffectively stops working due to the prevalence of bad data. Further,the monitoring system may explain, in quantitative or qualitative terms,how the current operation and/or the potential failure will affectoperation of the HVAC system. This enables the homeowner to prioritizeand budget for repairs.

For the monitoring service, the monitoring company may charge a periodicrate, such as a monthly rate. This charge may be billed directly to thehomeowner and/or may be billed to the contractor. The contractor maypass along these charges to the homeowner and/or may make otherarrangements, such as by requiring an up-front payment upon installationand/or applying surcharges to repairs and service visits.

For the air handler monitor and compressor monitor modules, themonitoring company or contractor may charge the homeowner the equipmentcost, including the installation cost, at the time of installationand/or may recoup these costs as part of the monthly fee. Alternatively,rental fees may be charged for the air handler monitor and compressormonitor modules, and once the monitoring service is stopped, the airhandler monitor and compressor monitor modules may be returned.

The monitoring service may allow a homeowner and/or contractor toremotely monitor and/or control HVAC components, such as settingtemperature, enabling or disabling heating and/or cooling, etc. Inaddition, the homeowner may be able to track energy usage, cycling timesof the HVAC system, and/or historical data. Efficiency and/or operatingcosts of the homeowner's HVAC system may be compared against HVACsystems of neighbors, whose homes will be subject to the sameenvironmental conditions. This allows for direct comparison of HVACsystem and overall home efficiency because environmental variables, suchas temperature and wind, are controlled.

The monitoring system can be used by the contractor during and afterinstallation and during and after repair to verify operation of the airhandler monitor and compressor monitor modules as well as to verifycorrect installation of the components of the HVAC system. In addition,the homeowner may review this data in the monitoring system forassurance that the contractor correctly installed and configured theHVAC system. In addition to being uploaded to the cloud, monitored datamay be transmitted to a local device in the residence. For example, asmartphone, laptop, or proprietary portable device may receivemonitoring information to diagnose problems and receive real-timeperformance data. Alternatively, data may be uploaded to the cloud andthen downloaded onto a local computing device, such as via the Internetfrom an interactive web site.

The historical data collected by the monitoring system may allow thecontractor to properly specify new HVAC components and to better tuneconfiguration, including dampers and set points of the HVAC system. Theinformation collected may be helpful in product development andassessing failure modes. The information may be relevant to warrantyconcerns, such as determining whether a particular problem is covered bya warranty. Further, the information may help to identify conditions,such as unauthorized system modifications, that could potentially voidwarranty coverage.

Original equipment manufacturers may subsidize partially or fully thecost of the monitoring system and air handler and compressor monitormodules in return for access to this information. Installation andservice contractors may also subsidize some or all of these costs inreturn for access to this information, and for example, in exchange forbeing recommended by the monitoring system. Based on historical servicedata and homeowner feedback, the monitoring system may providecontractor recommendations to homeowners.

Referring now to FIG. 2, a functional block diagram of an example systemshowing a single homeowner residence 300 is presented. The homeownerresidence 300 includes, for example only, a split system with an airhandler unit 304 and a compressor/condenser unit 308. Thecompressor/condenser unit 308 includes a compressor, a condenser, acondenser fan, and associated electronics. In many systems, the airhandler unit 304 is located inside the homeowner residence 300, whilethe compressor/condenser unit 308 is located outside the homeownerresidence 300, such as in an outdoor enclosure 312.

The present disclosure is not limited, and applies to other systemsincluding, as examples only, systems where the components of the airhandler unit 304 and the compressor/condenser unit 308 are located inclose proximity to each other or even in a single enclosure. The singleenclosure may be located inside or outside of the homeowner residence300. In various implementations, the air handler unit 304 may be locatedin a basement, garage, or attic. In ground source systems, where heat isexchanged with the earth, the air handler unit 304 and thecompressor/condenser unit 308 may be located near the earth, such as ina basement, crawlspace, garage, or on the first floor, such as when thefirst floor is separated from the earth by only a concrete slab.

According to the principles of the present disclosure, a compressormonitor module 316 is interconnected with the compressor/condenser unit308, and may be located within or in close proximity to the outdoorenclosure 312. The compressor monitor module 316 monitors parameters ofthe compressor/condenser unit 308 including current, voltage, andtemperatures.

In one implementation, the current measured is a single power supplycurrent that represents the aggregate current draw of the entire outdoorenclosure 312 from an electrical panel 318. A current sensor 320measures the current supplied to the compressor/condenser unit 308 andprovides measured data to the compressor monitor module 316. For exampleonly, the compressor/condenser unit 308 may receive an AC line voltageof approximately 240 volts. The current sensor 320 may sense current ofone of the legs of the 240 volt power supply. A voltage sensor (notshown) may sense the voltage of one or both of the legs of the ACvoltage supply. The current sensor 320 may include a currenttransformer, a current shunt, and/or a hall effect device. In variousimplementations, a power sensor may be used in addition to or in placeof the current sensor 320. Current may be calculated based on themeasured power, or profiles of the power itself may be used to evaluateoperation of components of the compressor/condenser unit 308.

An air handler monitor module 322 monitors the air handler unit 304. Forexample, the air handler monitor module 322 may monitor current,voltage, and various temperatures. In one implementation, the airhandler monitor module 322 monitors an aggregate current drawn by theentire air handler unit 304, and when the air handler unit 304 providespower to an HVAC control module 360, also the current drawn by the HVACcontrol module 360. A current sensor 324 measures current delivered tothe air handler unit 304 by the electrical panel 318. The current sensor324 may be similar to the current sensor 320. Voltage sensors (notshown) may be located near the current sensors 324 and 320. The voltagesensors provide voltage data to the air handler unit 304 and thecompressor/condenser unit 308.

The air handler unit 304 and the compressor/condenser unit 308 mayevaluate the voltage to determine various parameters. For example,frequency, amplitude, RMS voltage and DC offset may be calculated basedon the measured voltage. In situations where 3-phase power is used, theorder of the phases may be determined. Information about when thevoltage crosses zero may be used to synchronize various measurements andto determine frequency based on counting the number of zero crossingswithin a predetermine time period.

The air handler unit 304 includes a blower, a burner, and an evaporator.In various implementations, the air handler unit 304 includes anelectrical heating device instead of or in addition to the burner. Theelectrical heating device may provide backup or secondary heat. Thecompressor monitor module 316 and the air handler monitor module 322share collected data with each other. When the current measured is theaggregate current draw, in either the air handler monitor module 322 orthe compressor monitor module 316, contributions to the current profileare made by each component. It may be difficult, therefore, to easilydetermine in the time domain how the measured current corresponds toindividual components. However, when additional processing is available,such as in a monitoring system, which may include server and othercomputing resources, additional analysis, such as frequency domainanalysis, can be performed.

The frequency domain analysis may allow individual contributions of HVACsystem components to be determined. Some of the advantages of using anaggregate current measurement may include reducing the number of currentsensors that would otherwise be necessary to monitor each of the HVACsystem components. This reduces bill of materials costs, as well asinstallation costs and potential installation problems. Further,providing a single time domain current stream may reduce the amount ofbandwidth necessary to upload the current data. Nevertheless, thepresent disclosure could also be used with additional current sensors.

Further, although not shown in the figures, additional sensors, such aspressure sensors, may be included and connected to the air handlermonitor module 322 and/or the compressor monitor module 316. Thepressure sensors may be associated with return air pressure or supplyair pressure, and/or with pressures at locations within the refrigerantloop. Air flow sensors may measure mass air flow of the supply airand/or the return air. Humidity sensors may measure relative humidity ofthe supply air and/or the return air, and may also measure ambienthumidity inside or outside the homeowner residence 300.

In various implementations, the principles of the present disclosure maybe applied to monitoring other systems, such as a hot water heater, aboiler heating system, a refrigerator, a refrigeration case, a poolheater, a pool pump/filter, etc.. As an example, the hot water heatermay include an igniter, a gas valve (which may be operated by asolenoid), an igniter, an inducer blower, and a pump. Aggregate currentreadings can be analyzed by the monitoring company to assess operationof the individual components of the hot water heater. Aggregate loads,such as the hot water heater or the air handler unit 304, may beconnected to an AC power source via a smart outlet, a smart plug, or ahigh amp load control switch, each of which may provide an indicationwhen a connected device is activated.

In one implementation, which is shown in FIG. 2, the compressor monitormodule 316 provides data to the air handler monitor module 322, and theair handler monitor module 322 provides data from both the air handlermonitor module 322 and the compressor monitor module 316 to a remotemonitoring system 330. The monitoring system 330 is reachable via adistributed network such as the Internet 334. Alternatively, any othersuitable network, such as a wireless mesh network or a proprietarynetwork, may be used.

In various other implementations, the compressor monitor module 316 maytransmit data from the air handler monitor module 322 and the compressormonitor module 316 to an external wireless receiver. The externalwireless receiver may be a proprietary receiver for a neighborhood inwhich the homeowner residence 300 is located, or may be aninfrastructure receiver, such as a metropolitan area network (such asWiMAX), a WiFi access point, or a mobile phone base station.

In the implementation of FIG. 2, the air handler monitor module 322relays data between the compressor monitor module 316 and the monitoringsystem 330. For example, the air handler monitor module 322 may accessthe Internet 334 using a router 338 of the homeowner. The homeownerrouter 338 may already be present to provide Internet access to otherdevices within the homeowner residence 300, such as a homeowner computer342 and/or various other devices having Internet connectivity, such as aDVR (digital video recorder) or a video gaming system.

The air handler monitor module 322 may communicate with the homeownerrouter 338 via a gateway 346. The gateway 346 translates informationreceived from the air handler monitor module 322 into TCP/IP(Transmission Control Protocol/Internet Protocol) packets and viceversa. The gateway 346 then forwards those packets to the homeownerrouter 338. The gateway 346 may connect to the homeowner router 338using a wired or wireless connection. The air handler monitor module 322may communicate with the gateway 346 using a wired or wirelessconnection. For example, the interface between the gateway 346 and thehomeowner router 338 may be Ethernet (IEEE 802.3) or WiFi (IEEE 802.11).

The interface between the air handler monitor module 322 and the gateway346 may include a wireless protocol, such as Bluetooth, ZigBee (IEEE802.15.4), 900 Megahertz, 2.4 Gigahertz, WiFi (IEEE 802.11), andproprietary protocols. The air handler monitor module 322 maycommunicate with the compressor monitor module 316 using wired orwireless protocols. For example only, the air handler monitor module 322and the compressor monitor module 316 may communicate using power linecommunications, which may be sent over a line voltage (such as 240volts) or a stepped-down voltage, such as 24 volts, or a dedicatedcommunications line.

The air handler monitor module 322 and the compressor monitor module 316may transmit data within frames conforming to the ClimateTalk™ standard,which may include the ClimateTalk Alliance HVAC Application Profilev1.1, released Jun. 23, 2011, the ClimateTalk Alliance GenericApplication Profile, v1.1, released Jun. 23, 2011, and the ClimateTalkAlliance Application Specification, v1.1, released Jun. 23, 2011, thedisclosures of which are hereby incorporated by reference in theirentirety. In various implementations, the gateway 346 may encapsulateClimateTalk™ frames into IP packets, which are transmitted to themonitoring system 330. The monitoring system 330 then extracts theClimateTalk™ frames and parses the data contained within theClimateTalk™ frames. The monitoring system 330 may send returninformation, including monitoring control signals and/or HVAC controlsignals, using ClimateTalk™.

The HVAC control module 360 controls operation of the air handler unit304 and the compressor/condenser unit 308. The HVAC control module 360may operate based on control signals from a thermostat 364. Thethermostat 364 may transmit requests for fan, heat, and cool to the HVACcontrol module 360. One or more of the control signals may beintercepted by the air handler monitor module 322. Variousimplementations of interaction between the control signals and the airhandler monitor module 322 are shown below in FIGS. 3A-3C.

Additional control signals may be present in various HVAC systems. Forexample only, a heat pump may include additional control signals, suchas a control signal for a reversing valve. The thermostat 364 and/or theHVAC control module 360 may include control signals for secondaryheating and/or secondary cooling, which may be activated when theprimary heating or primary cooling is insufficient. In dual fuelsystems, such as systems operating from either electricity or naturalgas, control signals related to the selection of the fuel may bemonitored. Further, additional status and error signals may bemonitored, such as a defrost status signal, which may be asserted whenthe compressor is shut off and a defrost heater operates to melt frostfrom an evaporator.

In various implementations, the thermostat 364 may use the gateway 346to communicate with the Internet 334. In one implementation, thethermostat 364 does not communicate directly with the air handlermonitor module 322 or the compressor monitor module 316. Instead, thethermostat 364 communicates with the monitoring system 330, which maythen provide information or control signals to the air handler monitormodule 322 and/or the compressor monitor module 316 based on informationfrom the thermostat 364. Using the monitoring system 330, the homeowneror contractor may send signals to the thermostat 364 to manually enableheating or cooling (regardless of current temperature settings), or tochange set points, such as desired instant temperature and temperatureschedules. In addition, information from the thermostat 364, such ascurrent temperature and historical temperature trends, may be viewed.

The monitoring system 330 may provide alerts for situations such asdetected or predicted failures to the homeowner computer 342 and/or toany other electronic device of the homeowner. For example, themonitoring system 330 may provide an alert to a mobile device 368 of thehomeowner, such as a mobile phone or a tablet. The alerts are shown inFIG. 2 with dashed lines indicating that the alerts may not traveldirectly to the homeowner computer 342 or the mobile device 368 but maytraverse, for example, the Internet 334 and/or a mobile provider network(not shown). The alerts may take any suitable form, including textmessages, emails, social networking messages, voicemails, phone calls,etc.

The monitoring system 330 also interacts with a contractor computer 372.The contractor computer 372 may then interface with mobile devicescarried by individual contractors. Alternatively, the monitoring system330 may directly provide alerts to predetermined mobile devices of thecontractor. In the event of an impending or detected failure, themonitoring system 330 may provide information regarding identificationof the homeowner, identification of the HVAC system, the part or partsrelated to the failure, and/or the skills required to perform themaintenance.

In various implementations, the monitoring system 330 may transmit aunique identifier of the homeowner or the residence to the contractorcomputer 372. The contractor computer 372 may include a database indexedby the unique identifier, which stores information about the homeownerincluding the homeowner's address, contractual information such asservice agreements, and detailed information about the installed HVACequipment.

The air handler monitor module 322 and the compressor monitor module 316may receive respective sensor signals, such as water sensor signals. Forexample, the air handler monitor module 322 may receive signals from afloat switch 376, a condensate sensor 380, and a conduction sensor 384.The condensate sensor 380 may include a device as described in commonlyassigned patent application Ser. No. 13/162,798, filed Jun. 17, 2011,titled Condensate Liquid Level Sensor and Drain Fitting, the disclosureof which is hereby incorporated by reference in its entirety.

Where the air handler unit 304 is performing air conditioning,condensation occurs and is captured in a condensate pan. The condensatepan drains, often via a hose, into a floor drain or a condensate pump,which pumps the condensate to a suitable drain. The condensate sensor380 detects whether the drain hose has been plugged, a condition whichwill eventually cause the condensate pan to overflow, potentiallycausing damage to the HVAC system and to surrounding portions of thehomeowner residence 300.

The air handler unit 304 may be located on a catch pan, especially insituations where the air handler unit 304 is located above living spaceof the homeowner residence 300. A catch pan may include the float switch376. When enough liquid accumulates in the catch pan, the float switch376 provides an over-level signal to the air handler monitor module 322.

The conduction sensor 384 may be located on the floor or other surfacewhere the air handler unit 304 is located. The conduction sensor 384 maysense water leaks that are for one reason or another not detected by thefloat switch 376 or the condensate sensor 380, including leaks fromother systems such as a hot water heater.

Referring now to FIG. 3A, an example of control signal interaction withthe air handler monitor module 322 is presented. In this example, theair handler monitor module 322 taps into the fan and heat requestsignals. For example only, the HVAC control module 360 may includeterminal blocks where the fan and heat signals are received. Theseterminals blocks may include additional connections where leads can beattached between these additional connections and the air handlermonitor module 322.

Alternatively, leads from the air handler monitor module 322 may beattached to the same location as the fan and heat signals, such as byputting multiple spade lugs underneath a signal screw head. The coolsignal from the thermostat 364 may be disconnected from the HVAC controlmodule 360 and attached to the air handler monitor module 322. The airhandler monitor module 322 then provides a switched cool signal to theHVAC control module 360. This allows the air handler monitor module 322to interrupt operation of the air conditioning system, such as upondetection of water by one of the water sensors. The air handler monitormodule 322 may also interrupt operation of the air conditioning systembased on information from the compressor monitor module 316, such asdetection of a locked rotor condition in the compressor.

Referring now to FIG. 3B, the fan, heat, and cool signals are connectedto the air handler monitor module 322 instead of to the HVAC controlmodule 360. The air handler monitor module 322 then provides fan, heat,and switched cool signals to the HVAC control module 360. In variousother implementations, the air handler monitor module 322 may alsoswitch the fan and/or heat signals.

Referring now to FIG. 3C, the thermostat 400 may use a proprietary ordigital form of communication instead of discrete request lines such asthose used by the thermostat 364. Especially in installations where thethermostat 400 is added after the HVAC control module 360 has beeninstalled, an adapter 404 may translate the proprietary signals intoindividual fan, heat, and cool request signals. The air handler monitormodule 322 can then be connected similarly to FIG. 3A (as shown) or FIG.3B.

Referring now to FIG. 4A, a functional block diagram of an exampleimplementation of the air handler monitor module 322 is presented. Acontrol line monitor module 504 receives the fan, heat, and cool requestsignals. A compressor interrupt module 508 also receives the coolrequest signal. Based on a disable signal, the compressor interruptmodule 508 deactivates the switched cool signal. Otherwise, thecompressor interrupt module 508 may pass the cool signal through as theswitched cool signal.

The control line monitor module 504 may also receive additional controlsignals, depending on application, including second stage heat, secondstage cool, reversing valve direction, defrost status signal, and dualfuel selection.

A wireless transceiver 512 communicates using an antenna 516 with awireless host, such as a gateway 346, a mobile phone base station, or aWiFi (IEEE 802.11) or WiMax (IEEE 802.16) base station. A formattingmodule 520 forms data frames, such as ClimateTalk™ frames, includingdata acquired by the air handler monitor module 322. The formattingmodule 520 provides the data frames to the wireless transceiver 512 viaa switching module 524.

The switching module 524 receives data frames from the monitoring system330 via the wireless transceiver 512. Additionally or alternatively, thedata frames may include control signals. The switching module 524provides the data frames received from the wireless transceiver 512 tothe formatting module 520. However, if the data frames are destined forthe compressor monitor module 316, the switching module 524 may insteadtransmit those frames to a power-line communication module 528 fortransmission to the compressor monitor module 316.

A power supply 532 provides power to some or all of the components ofthe air handler monitor module 322. The power supply 532 may beconnected to line voltage, which may be single phase 120 volt AC power.Alternatively, the power supply 532 may be connected to a stepped downvoltage, such as a 24 volt power supply already present in the HVACsystem. When the power received by the power supply 532 is also providedto the compressor monitor module 316, the power-line communicationmodule 528 can communicate with the compressor monitor module 316 viathe power supply 532. In other implementations, the power supply 532 maybe distinct from the power-line communication module 528. The power-linecommunication module 528 may instead communicate with the compressormonitor module 316 using another connection, such as the switched coolsignal (which may be a switched 24 volt line) provided to the compressormonitor module 316, another control line, a dedicated communicationsline, etc.

In various implementations, power to some components of the air handlermonitor module 322 may be provided by 24 volt power from the thermostat364. For example only, the cool request from the thermostat 364 mayprovide power to the compressor interrupt module 508. This may bepossible when the compressor interrupt module 508 does not need tooperate (and therefore does not need to be powered) unless the coolrequest is present, thereby powering the compressor interrupt module508.

Data frames from the compressor monitor module 316 are provided to theswitching module 524, which forwards those frames to the wirelesstransceiver 512 for transmission to the gateway 346. In variousimplementations, data frames from the compressor monitor module 316 arenot processed by the air handler monitor module 322 other than toforward the frames to the gateway 346. In other implementations, the airhandler monitor module 322 may combine data gathered by the air handlermonitor module 322 with data gathered by the compressor monitor module316 and transmit combined data frames.

In addition, the air handler monitor module 322 may perform datagathering or remedial operations based on the information from thecompressor monitor module 316. For example only, the compressor monitormodule 316 may transmit a data frame to the air handler monitor module322 indicating that the air handler monitor module 322 should monitorvarious inputs. For example only, the compressor monitor module 316 maysignal that the compressor is about to start running or has startedrunning. The air handler monitor module 322 may then monitor relatedinformation.

Therefore, the formatting module 520 may provide such a monitoringindication from the compressor monitor module 316 to a trigger module536. The trigger module 536 determines when to capture data, or if datais being continuously captured, which data to store, process, and/orforward data. The trigger module 536 may also receive a signal from anerror module 540. The error module 540 may monitor an incoming currentand generate an error signal when the current is at too high of a levelfor too long of a time.

The compressor monitor module 316 may be configured similarly to the airhandler monitor module 322. In the compressor monitor module 316, acorresponding error module may determine that a high current levelindicates a locked rotor condition of the compressor. For example only,a baseline run current may be stored, and a current threshold calculatedby multiplying the baseline run current by a predetermined factor. Thelocked rotor condition may then be determined when a measurement ofcurrent exceeds the current threshold. This processing may occur locallybecause a quick response time to a locked rotor is beneficial.

The error module 540 may instruct the trigger module 536 to captureinformation to help diagnose this error and/or may send a signal to thecompressor interrupt module 508 to disable the compressor. The disablesignal received by the compressor interrupt module 508 may causedisabling of the compressor interrupt module 508 when either the errormodule 540 or the formatting module 520 indicates that the interruptionis required. This logical operation is illustrated with an OR gate 542.

The formatting module 520 may disable the compressor based on aninstruction from the monitoring system 330 and/or the compressor monitormodule 316. For example, the monitoring system 330 may instruct theformatting module 520 to disable the compressor based on a request by autility company. For example, during peak load times, the utilitycompany may request air conditioning to be turned off in return for adiscount on electricity prices. This shut off can be implemented via themonitoring system 330.

A water monitoring module 544 may monitor the conduction sensor 384, thefloat switch 376, and the condensate sensor 380. For example, when aresistivity of the conduction sensor 384 decreases below a certainvalue, which would happen in the presence of water, the water monitoringmodule 544 may signal to the error module 540 that water is present.

The water monitoring module 544 may also detect when the float switch376 detects excessive water, which may be indicated by a closing or anopening of the float switch 376. The water monitoring module 544 mayalso detect when resistivity of the condensate sensor 380 changes. Invarious implementations, detection of the condensate sensor 380 may notbe armed until a baseline current reading is made, such as at the timewhen the air handler monitor module 322 is powered on. Once thecondensate sensor 380 is armed, a change in current may be interpretedas an indication that a blockage has occurred. Based on any of thesewater signals, the water monitoring module 544 may signal to the errormodule 540 that the compressor should be disabled.

A temperature tracking module 548 tracks temperatures of one or moreHVAC components. For example, the temperature tracking module 548 maymonitor the temperature of supply air and of return air. The temperaturetracking module 548 may provide average values of temperature to theformatting module 520. For example only, the averages may be runningaverages. The filter coefficients of the running averages may bepredetermined and may be modified by the monitoring system 330.

The temperature tracking module 548 may monitor one or more temperaturesrelated to the air conditioning system. For example, a liquid lineprovides refrigerant to an expansion valve of the air handler unit 304from a condenser of the compressor/condenser unit 308. A temperature maybe measured along the refrigerant line before and/or after the expansionvalve. The expansion valve may include, for example, a thermostaticexpansion valve, a capillary tube, or an automatic expansion valve.

The temperature tracking module 548 may additionally or alternativelymonitor one or more temperatures of an evaporator coil of the airhandler unit 304. The temperatures may be measured along the refrigerantline at or near the beginning of the evaporator coil, at or near an endof the evaporator coil, or at one or more midpoints. In variousimplementations, the placement of the temperature sensor may be dictatedby physical accessibility of the evaporator coil. The temperaturetracking module 548 may be informed of the location of the temperaturesensor. Alternatively, data about temperature location may be stored aspart of installation data, which may be available to the formattingmodule 520 and/or to the monitoring system, which can use thisinformation to accurately interpret the received temperature data.

A power calculation module 552 monitors voltage and current. In oneimplementation, these are the aggregate power supply voltage and theaggregate power supply current, which represents the total currentconsumed by all of the components of the air handler unit 304. The powercalculation module 552 may perform a point-by-point power calculation bymultiplying the voltage and current. Point-by-point power values and/oran average value of the point-by-point power is provided to theformatting module 520.

A current recording module 556 records values of the aggregate currentover a period of time. The aggregate current may be sensed by a currentsensor that is installed within the air handler unit 304 or along theelectrical cable providing power to the air handler unit 304 (seecurrent sensor 324 In FIG. 2). For example only, the current sensor maybe located at a master switch that selectively supplies the incomingpower to the air handler unit 304. Alternatively, the current sensor maybe located closer to, or inside of, an electrical distribution panel.The current sensor may be installed in line with one or more of theelectrical wires feeding current from the electrical distribution panelto the air handler unit 304.

The aggregate current includes current drawn by all energy consumingcomponents of the air handler unit 304. For example only, the energyconsuming components can include a gas valve solenoid, an igniter, acirculator blower motor, an inducer blower motor, a secondary heatsource, an expansion valve controller, a furnace control panel, acondensate pump, and a transformer, which may provide power to athermostat. The energy consuming components may also include the airhandler monitor module 322 itself and the compressor monitor module 316.

It may be difficult to isolate the current drawn by any individualenergy consuming component. Further, it may be difficult to quantify orremove distortion in the aggregate current, such as may be caused byfluctuations of the voltage level of incoming AC power. As a result,processing is applied to the current, which includes, for example only,filtering, statistical processing, and frequency domain processing.

In the implementation of FIG. 4A, the time domain series of currentsfrom the current recording module 556 is provided to a fast Fouriertransform (FFT) module 560, which generates a frequency spectrum fromthe time domain current values. The length of time and the frequencybins used by the FFT module 560 may be configurable by the monitoringsystem 330. The FFT module 560 may include, or be implemented by, adigital signal processor (DSP). In various implementations, the FFTmodule 560 may perform a discrete Fourier transform (DFT). The currentrecording module 556 may also provide raw current values, an averagecurrent value (such as an average of absolute values of the current), oran RMS current value to the formatting module 520.

A clock 564 allows the formatting module 520 to apply a time stamp toeach data frame that is generated. In addition, the clock 564 may allowthe trigger module 536 to periodically generate a trigger signal. Thetrigger signal may initiate collection and/or storage and processing ofreceived data. Periodic generation of the trigger signal may allow themonitoring system 330 to receive data from the air handler monitormodule 322 frequently enough to recognize that the air handler monitormodule 322 is still functioning.

A voltage tracking module 568 measures the AC line voltage, and mayprovide raw voltage values or an average voltage value (such as anaverage of absolute values of the voltage) to the formatting module 520.Instead of average values, other statistical parameters may becalculated, such as RMS (root mean squared) or mean squared.

Based on the trigger signal, a series of frames may be generated andsent. For example only, the frames may be generated contiguously for 105seconds and then intermittently for every 15 seconds until 15 minuteshas elapsed. Each frame may include a time stamp, RMS voltage, RMScurrent, real power, average temperature, conditions of status signals,status of liquid sensors, FFT current data, and a flag indicating thesource of the trigger signal. Each of these values may correspond to apredetermined window of time, or, frame length.

The voltage and current signals may be sampled by an analog-to-digitalconverter at a certain rate, such as 1920 samples per second. The framelength may be measured in terms of samples. When a frame is 256 sampleslong, at a sample rate of 1920 samples per second, there are 7.5 framesevery second (or, 0.1333 seconds per frame). Generation of the triggersignal is described in more detail below in FIG. 7. The sampling rate of1920 Hz has a Nyquist frequency of 960 Hz and therefore allows an FFTbandwidth of up to approximately 960 Hz. An FFT limited to the time spanof a single frame may be calculated by the FFT module 560 for each ofthe frames.

The formatting module 520 may receive a request for a single frame fromthe monitoring system 330. The formatting module 520 therefore providesa single frame in response to the request. For example only, themonitoring system 330 may request a frame every 30 seconds or some otherperiodic interval, and the corresponding data may be provided to acontractor monitoring the HVAC system in real time.

Referring now to FIG. 4B, an example implementation of the compressormonitor module 316 is shown. Components of the compressor monitor module316 may be similar to components of the air handler monitor module 322of FIG. 4A. For example only, the compressor monitor module 316 mayinclude the same hardware components as the air handler monitor module322, where unused components, such as the wireless transceiver 512, aresimply disabled or deactivated. In various other implementations, acircuit board layout may be shared between the air handler monitormodule 322 and the compressor monitor module 316, with various locationson the printed circuit board being depopulated (corresponding tocomponents present in the air handler monitor module 322 but notimplemented in the compressor monitor module 316).

The current recording module 556 of FIG. 4B receives an aggregatecurrent value (such as from current sensor 320 of FIG. 2) thatrepresents the current to multiple energy consuming components of thecompressor/condenser unit 308. The energy consuming components mayinclude start windings, run windings, capacitors, and contactors/relaysfor a condenser fan motor and a compressor motor. The energy consumingcomponents may also include a reversing valve solenoid, a control board,and in some implementations the compressor monitor module 316 itself.

In the compressor monitoring module 316, the temperature tracking module548 may track an ambient temperature. When the compressor monitor module316 is located outdoors, the ambient temperature represents an outsidetemperature. As discussed above, the temperature sensor supplying theambient temperature may be located outside of an enclosure housing acompressor or condenser. Alternatively, the temperature sensor may belocated within the enclosure, but exposed to circulating air. In variousimplementations the temperature sensor may be shielded from directsunlight and may be exposed to an air cavity that is not directly heatedby sunlight.

The temperature tracking module 548 may monitor temperatures of therefrigerant line at various points, such as before the compressor(referred to as a suction line temperature), after the compressor(referred to as a compressor discharge temperature), after the condenser(referred to as a liquid line out temperature), and/or at one or morepoints along the condenser coil. The location of temperature sensors maybe dictated by a physical arrangement of the condenser coils. Duringinstallation, the location of the temperature sensors may be recorded.

Additionally or alternatively, a database may be available thatspecifies where temperature sensors are placed. This database may bereferenced by installers and may allow for accurate cloud processing ofthe temperature data. The database may be used for both air handlersensors and compressor/condenser sensors. The database may beprepopulated by the monitoring company or may be developed by trustedinstallers, and then shared with other installation contractors. Thetemperature tracking module 548 and/or a cloud processing function maydetermine an approach temperature, which is a measurement of how closethe condenser has been able to make the liquid line out temperature tothe ambient air temperature.

Referring now to FIGS. 5A-5I, block diagrams of example implementationsof the air handler monitor module 322 are shown. Although the functionsdepicted in FIG. 4A may be performed by various circuitry blocks ofFIGS. 5A-5I, there may not be a one-to-one correspondence between thefunctional blocks of FIG. 4A and the circuitry blocks of any of FIGS.5A-5I.

Referring now to FIG. 5A, temperatures are received by signal scalingblocks 572-1, 572-2, and 572-3 (collectively, signal scaling blocks572). For example only, the signal scaling blocks 572 may includeresistive dividers and/or amplifiers to scale the input signalsappropriately and provide the scaled signals to analog-to-digital (A/D)converters 574-1, 574-2, and 574-3, respectively (collectively, A/Dconverters 574). A microprocessor 576 may include the A/D converters574. The microprocessor executes code from memory 578. Signal scalingblocks 572-4 and 572-5 scale voltage and current, respectively.

A power supply 580 provides power to components of the air handlermonitor module 322. A communications module 582 includes acommunications controller 584, a radio 586 for wireless communication,and a power line communications module 588 for power linecommunications. A power monitor chip 590 may monitor the scaled voltageand current and provide current and voltage information, as well aspower information and phase information, to the microprocessor 576.

Referring now to FIG. 5B, signal scaling blocks 572-6 and 572-7 receivethe voltage and current, respectively, and provide those values to amicroprocessor 592. For example only, the microprocessor 592 may includecomparators to determine zero-crossing events of the voltage and/orcurrent in response to the analog signals from the signal scaling blocks572-6 and 572-7. A/D converters 574-4 and 574-5 convert scaled voltageand current signals, respectively, into digital values that are providedto a microprocessor 592. In the implementation shown in FIG. 5B, the A/Dconverters 574-1, 574-2, and 574-3 are not integrated withmicroprocessor 592 and are instead stand-alone.

Although 10-bit and 12-bit A/D converters are shown, A/D convertershaving more or less resolution may be chosen. In variousimplementations, such as shown in FIG. 5B, higher-resolution A/Dconverters may be used for values, such as current and voltage, wherehigher precision is desired and where the source analog signalsthemselves are of higher precision.

Referring now to FIG. 5C, an implementation similar to that of FIG. 5Bis shown. In FIG. 5C, the A/D converters 574-1, 574-2, and 574-3 areintegrated in a microprocessor 594.

Referring now to FIG. 5D, programmable gain modules 596-1 and 596-2allow programmable gains to be applied to the voltage and current. Thismay allow for features such as automatic gain control. A microprocessor596 controls the programmable gain module 596-1 and 596-2 using a commonvalue or using individual values. In FIG. 5D, the A/D converters 574-4and 5745 are integrated in a microprocessor 596. In variousimplementations, the microprocessor 596 may offer only a certainresolution of A/D converters, such as 10-bit, in which case the A/Dconverters 574-4 and 574-5 may have 10-bit resolution instead of 12-bitresolution.

Referring now to FIG. 5E, a microprocessor 598 integrates thecommunications controller 584.

Referring now to FIG. 5F, a microprocessor 600 further integrates theA/D converters 574-4 and 574-5, and in this case, maintains the 12-bitresolution.

Referring now to FIG. 5G, a microprocessor 602 integrates the memory 578on chip. Additional memory (not shown) may be provided off chip.

Referring now to FIG. 5H, a custom integrated circuit 604 may integratemany of the functions described above, including the power supply 580,the power line communications module 588, the radio 586, and the memory578. The custom integrated circuit 604 includes a multiplexer 608, whichprovides sensed data to a microprocessor 606 over a multiplexed bus. Themicroprocessor 606 may also implement the communications controller 584.To provide voltage compatible with the custom integrated circuit 604, avoltage divider 616 is located prior to the voltage signal entering thecustom integrated circuit 604.

Referring now to FIG. 5I, a custom integrated circuit 630 may implementthe modules of the custom integrated circuit 604 of FIG. 5H as well asintegrating the microprocessor 606 by using a microprocessor core 640.

Referring now to FIG. 5J, a data flow diagram is shown for a monitoringmodule, such as the air handler monitor module 322. A power line 650supplies power to a power supply 652. The voltage of the power line 650is conditioned by a signal conditioning block 654 and then provided to avoltage log 656 and a power calculator 658. Zero crossings of thevoltage are monitored by a zero cross block 660 and transmitted to aphase calculation module 662. The phase calculation module 662determines phase difference between voltage and current based on zerocrossing information from the zero cross block 660 and a current zerocross block 664.

The current zero cross block 664 receives current from a current sensor666, which also provides current values to a signal conditioning block668, which conditions the current values, such as by applying filters,and provides them to a current monitor 670 and a power calculation block658. The power calculation block determines power based on the currentand voltage and supplies the result to a power log 674.

The current log 672, the power log 674, a phase log 676, and the voltagelog 656 provide information to an information packaging block 678. Theinformation packaging block 678 packages information for transmission bya transmit block 680. The information packaging block 678 may provideidentifying information such as a module ID number 682. A temperaturelog 684 receives one or more temperature signals 686, while a pressurelog 688 receives one or more pressures 690.

A key recognition block 692 monitors inputs from a variety of sources,which may include the power calculation block 658, the phase calculationblock 662, the voltage log 656, the temperature log 684, the pressurelog 688, and state inputs 694, such as call for heat and call for coolcontrol lines. The key recognition block 692 may identify which portionsof each of the logs is transmitted by the transmit block 680.

The key recognition block 692 identifies occurrence of certain events,such as the beginning of a call for heat or call for cool. In addition,the key recognition block 692 may recognize when anomalous situationshave occurred, such as over-voltage, over-current, or temperatures orpressures out of bounds. In response to identification of events by thekey recognition block 692, a log control block 694 may control theinformation packaging block 678 to discard or only locally store lowpriority information, to delay transmitting medium priority information,and to transmit higher priority information more quickly or evenimmediately.

Referring now to FIG. 6, a brief overview of an example monitoringsystem installation, such as in a retrofit application, is presented.Although FIGS. 6 and 7 are drawn with arrows indicating a specific orderof operation, the present disclosure is not limited to this specificorder. At 704, mains power to the air handler is disconnected. If thereis no outside disconnect for the mains power to the compressor/condenserunit, mains power to the compressor/condenser unit should also bedisconnected at this point. At 708, the cool line is disconnected fromthe HVAC control module and connected to the air handler monitor module.At 712, the switched cool line from the air handler monitor module isconnected to the HVAC control module where the cool line was previouslyconnected.

At 716, fan, heat, and common lines from the air handler monitor moduleare connected to terminals on the HVAC control module. In variousimplementations, the fan, heat, and common lines originally going to theHVAC control module may be disconnected and connected to the air handlermonitor module. This may be done for HVAC control modules whereadditional lines cannot be connected in parallel with the original fan,heat, and common lines.

At 720, a current sensor such as a snap-around current transformer, isconnected to mains power to the HVAC system. At 724, power and commonleads are connected to the HVAC transformer, which may provide 24 voltpower to the air handler monitor module. In various implementations, thecommon lead may be omitted, relying on the common lead discussed at 716.Continuing at 728, a temperature sensor is placed in the supply air ductwork and connected to the air handler monitor module. At 732, atemperature sensor is placed in the return air duct work and connectedto the air handler monitor module. At 734, a temperature sensor isplaced in a predetermined location, such as a middle loop, of theevaporator coil. At 736, water sensors are installed and connected tothe air handler monitor module.

At 740, mains power to the compressor/condenser unit is disconnected. At744, the power supply of the compressor monitor module is connected tothe compressor/condenser unit's input power. For example, the compressormonitor module may include a transformer that steps down the linevoltage into a voltage usable by the compressor monitor module. At 748,a current sensor is attached around the compressor/condenser unit'spower input. At 752, a voltage sensor is connected to thecompressor/condenser unit's power input.

At 756, a temperature sensor is installed on the liquid line, such as atthe input or the output to the condenser. The temperature sensor may bewrapped with insulation to thermally couple the temperature sensor tothe liquid in the liquid line and thermally isolate the temperaturesensor from the environment. At 760, the temperature sensor is placed ina predetermined location of the condenser coil and insulated. At 764,the temperature sensor is placed to measure ambient air. The temperaturesensor may be located outside of the outdoor enclosure 312 or in a spaceof the outdoor enclosure 312 in which outside air circulates. At 768,mains power to the air handler and the compressor/condenser unit isrestored.

Referring now to FIG. 7, a flowchart depicts example operation incapturing frames of data. Control begins upon startup of the air handlermonitor module at 800, where an alive timer is reset. The alive timerensures that a signal is periodically sent to the monitoring system sothat the monitoring system knows that the air handler monitor module isstill alive and functioning. In the absence of this signal, themonitoring system 330 will infer that the air handler monitor module ismalfunctioning or that there is connectivity issue between the airhandler monitor module and the monitoring system.

Control continues at 804, where control determines whether a request fora frame has been received from the monitoring system. If such a requesthas been received, control transfers to 808; otherwise, controltransfers to 812. At 808, a frame is logged, which includes measuringvoltage, current, temperatures, control lines, and water sensor signals.Calculations are performed, including averages, powers, RMS, and FFT.Then a frame is transmitted to the monitoring system. In variousimplementations, monitoring of one or more control signals may becontinuous. Therefore, when a remote frame request is received, the mostrecent data is used for the purpose of calculation.

Control then returns to 800. Referring now to 812, control determineswhether one of the control lines has turned on. If so, control transfersto 816; otherwise, control transfers to 820. Although 812 refers to thecontrol line being turned on, in various other implementations, controlmay transfer to 816 when a state of a control line changes—i.e., whenthe control line either turns on or turns off. This change in status maybe accompanied by signals of interest to the monitoring system. Controlmay also transfer to 816 in response to an aggregate current of eitherthe air handler unit or the compressor/condenser unit.

At 820, control determines whether a remote window request has beenreceived. If so, control transfers to 816; otherwise, control transfersto 824. The window request is for a series of frames, such as isdescribed below. At 824, control determines whether current is above athreshold, and if so, control transfers to 816; otherwise, controltransfers to 828. At 828, control determines whether the alive timer isabove a threshold such as 60 minutes. If so, control transfers to 808;otherwise, control returns to 804.

At 816, a window timer is reset. A window of frames is a series offrames, as described in more detail here. At 832, control begins loggingframes continuously. At 836, control determines whether the window timerhas exceeded a first threshold, such as 105 seconds. If so, controlcontinues at 840; otherwise, control remains at 836, logging framescontinuously. At 840, control switches to logging frames periodically,such as every 15 seconds.

Control continues at 844, where control determines whether the HVACsystem is still on. If so, control continues at 848; otherwise, controltransfers to 852. Control may determine that the HVAC system is on whenan aggregate current of the air handler unit and/or of the compressorunit exceeds a predetermined threshold. Alternatively, control maymonitor control lines of the air handler unit and/or the compressor unitto determine when calls for heat or cool have ended. At 848, controldetermines whether the window timer now exceeds a second threshold, suchas 15 minutes. If so, control transfers to 852; otherwise, controlreturns to 844 while control continues logging frames periodically.

At 852, control stops logging frames periodically and performscalculations such as power, average, RMS, and FFT. Control continues at856 where the frames are transmitted. Control then returns to 800.Although shown at the end of frame capture, 852 and 856 may be performedat various times throughout logging of the frames instead of at the end.For example only, the frames logged continuously up until the firstthreshold may be sent as soon as the first threshold is reached. Theremaining frames up until the second threshold is reached may each besent out as it is captured.

In various implementations, the second threshold may be set to a highvalue, such as an out of range high, which effectively means that thesecond threshold will never be reached. In such implementations, theframes are logged periodically for as long as the HVAC system remainson.

A server of the monitoring system includes a processor and memory, wherethe memory stores application code that processes data received from theair handler monitor and compressor monitor modules and determinesexisting and/or impending failures, as described in more detail below.The processor executes this application code and stores received dataeither in the memory or in other forms of storage, including magneticstorage, optical storage, flash memory storage, etc. While the termserver is used in this application, the application is not limited to asingle server.

A collection of servers, which may together operate to receive andprocess data from the air handler monitor and compressor monitor modulesof multiple residences. A load balancing algorithm may be used betweenthe servers to distribute processing and storage. The presentapplication is not limited to servers that are owned, maintained, andhoused by a monitoring company. Although the present disclosuredescribes diagnostics and processing and alerting occurring in themonitoring system 330, some or all of these functions may be performedlocally using installed equipment and/or homeowner resources, such as ahomeowner computer.

The servers may store baselines of frequency data for the HVAC system ofa residence. The baselines can be used to detect changes indicatingimpending or existing failures. For example only, frequency signaturesof failures of various components may be pre-programmed, and may beupdated based on observed evidence from contractors. For example, once amalfunctioning HVAC system has been diagnosed, the monitoring system maynote the frequency data leading up to the malfunction and correlate thatfrequency signature with the diagnosed cause of the malfunction. Forexample only, a computer learning system, such as a neural network or agenetic algorithm, may be used to refine frequency signatures. Thefrequency signatures may be unique to different types of HVAC systemsand/or may share common characteristics. These common characteristicsmay be adapted based on the specific type of HVAC system beingmonitored.

The monitoring system may also receive current data in each frame. Forexample, when 7.5 frames per seconds are received, current data having a7.5 Hz resolution is available. The current and/or the derivative ofthis current may be analyzed to detect impending or existing failures.In addition, the current and/or the derivative may be used to determinewhen to monitor certain data, or points at which to analyze obtaineddata. For example, frequency data obtained at a predetermined windowaround a certain current event may be found to correspond to aparticular HVAC system component, such as activation of a hot surfaceigniter.

Components of the present disclosure may be connected to meteringsystems, such as utility (including gas and electric) metering systems.Data may be uploaded to the monitoring system 330 using any suitablemethod, including communications over a telephone line. Thesecommunications may take the form of digital subscriber line (DSL) or mayuse a modem operating at least partially within vocal frequencies.Uploading to the monitoring system 330 may be confined to certain timesof day, such as at night time or at times specified by the contractor orhomeowner. Further, uploads may be batched so that connections can beopened and closed less frequently. Further, in various implementations,uploads may occur only when a fault or other anomaly has been detected.

Methods of notification are not restricted to those disclosed above. Forexample, notification of HVAC problems may take the form of push or pullupdates to an application, which may be executed on a smart phone orother mobile device or on a standard computer. Notifications may also beviewed using web applications or on local displays, such as thethermostat 364 or other displays located throughout the residence or onthe air handler monitor module 322 or the compressor monitor module 316.

Referring now to FIG. 8, a functional schematic of example HVACcomponents is shown. An air conditioning unit controller 902 receivespower from a first power line 904, a second power line 906, and aneutral line 908 (also called a center tap CT). Current sensors 910measure current arriving on the first power line 904 and the secondpower line 906. A condenser fan 912 is controlled by a switch 914. Acurrent sensor 916 that monitors current to the condenser fan may beeliminated according to the principles of the present disclosure.

A compressor motor 918 includes a start winding 920 and a run winding922 and is controlled by a switch 924. A run capacitor 926 may beconnected across terminals of the compressor motor 918. Current sensors928, 930, and 931, which measure currents supplied to the compressormotor 918, may be eliminated in accordance with the principles of thepresent disclosure. A mid-capacity solenoid 932 may be actuated by aswitch 934. The mid-capacity solenoid 932 may alter the capacity of thecompressor motor 918, for example from a high capacity to a mediumcapacity.

A reversing valve 936 may be controlled by a switch 938 and/or by aswitch 940. A processor 942 controls switches 914, 924, 934, 938, and940. The processor 942 may provide visual indicators of operation, suchas on a screen or via a blinking multicolor light-emitting diode 944.The processor 942 may communicate with a furnace control processor 946via a network port 948 over networking lines 950. The processor 942 mayoperate in response to a high side refrigerant processor 952 and a lowside refrigerant processor 954. The processor 942 may also operate inresponse to an outside ambient temperature sensor 956 and a condensercoil temperature sensor 958.

A blower motor controller 960 communicates over the network using thenetworking lines 950. The blower motor controller 960 may include ablower control processor 962 and a inverter driver 964. The inverterdriver 964 drives a circulator blower motor 966. A circulator blowercontroller 968 controls the blower motor controller 960 over the networkusing the networking lines 950. The circulator blower controllerincludes a relay 970 and a circulator control processor 972.

A furnace controller 974 includes the furnace control processor 946 andswitches 976, 978, and 980. The furnace controller 974 receives powerfrom one of the lines 904 or 906 and the neutral line 908. The furnacecontrol processor 946 receives control signals from a thermostat 982 andactuates the switches 976, 978, and 980 in response. The switch 976 maybe a relay and controls a gas valve 984, which regulates combustion fuelto the furnace. The switch 978 controls an inducer motor 986, whichexhausts combustion gases. The switch 980 controls an igniter 988, whichignites the fuel. The furnace controller 974 and the thermostat 982 arepowered by a transformer 990.

Referring now to FIG. 9, an aggregate current level begins at a non-zerocurrent 1004 indicating that at least one energy consuming component isconsuming energy. A spike in current 1008 may indicate that anothercomponent is turning on. Elevated current 1012 may correspond tooperation of the inducer blower. This is followed by a spike 1016, whichmay indicate the beginning of operation of a hot surface igniter. Afteropening of a solenoid-operated gas valve, the hot surface igniter mayturn off, which returns current to a level corresponding to the inducerblower at 1018. The current may remain approximately flat 1020 until acurrent ramp 1024 begins, indicating the beginning of circulator bloweroperation. A spike 1028 may indicate transition from starting to runningof the circulator blower.

Referring now to FIG. 10A, another example current trace begins at 1050.A spike at 1054 indicates operation of a component, such as a hotsurface igniter. Transitions at 1058 and 1062 may indicate operation ofother energy consuming components or operating changes of the hotsurface igniter. A spike 1066 may indicate the beginning of operation ofanother energy consuming component, such as a circulator blower.

Referring now to FIG. 10B, the transitions shown in FIG. 10A may beisolated to allow the data at these transitions to be carefullyinspected, as the data at these times may have greater diagnostic value.In order to identify transitions, such as 1054, 1058, 1062, and 1066,mathematical algorithms, which may include averages and derivatives, areapplied to the current trace of FIG. 10A to produce corresponding spikes1080, 1084, 1088, and 1092.

Referring now to FIG. 10C, another example current trace is shown. Whilethe current trace of FIG. 10C is visually different from that of FIG.10A, it may be difficult to quantify this difference. It may beespecially difficult to develop a universal pattern for distinguishingthe current trace of FIG. 10C from the current trace of FIG. 10A. Thecurrent trace of FIG. 10C may represent a change in operation, such asdegradation of the hot surface igniter. In order to more clearlydistinguish FIG. 10C from FIG. 10A, frequency domain analysis may beused.

Referring now to FIG. 11A, a bar chart 1100 depicts relative frequencycontent in each of 33 frequency bins, which is obtained by a frequencydomain analysis of FIG. 10A. For example only, an FFT was performed overa specified period of the time domain trace of FIG. 10A. For exampleonly, the specified time may be keyed to one of the transitionsidentified in FIG. 10B.

Referring now to FIG. 11B, the bar chart 1104 depicts frequency contentcorresponding to the time domain trace of FIG. 10C. Referring now toFIG. 11 C, a comparison between the frequency domain data of FIGS. 11Aand 11B is shown. In various implementations, this difference may becalculated simply by subtracting, bin by bin, the value of FIG. 11 Bfrom the value of FIG. 11A. The resulting frequency domain data 1108 maybe indicative of a failing igniter. For example only, when certainfrequency bins in the difference spectrum 1108 exceed a certainthreshold, the monitoring system may determine that the igniter hasfailed or is failing.

Referring now to FIG. 12A, an example current trace has an approximatelyconstant level 1140 until a spike 1144 indicates operation of a hotsurface igniter. A second spike 1148 indicates actuation of asolenoid-operated gas valve. Referring now to FIG. 12B, another examplecurrent trace shows operation of the hot surface igniter that appears tobe missing operation of the solenoid-operated gas valve. Referring nowto FIG. 12C, a frequency domain analysis is performed on both FIG. 12Aand FIG. 12B, and a difference spectrum between the two frequency domainspectra is shown in FIG. 12C. This frequency domain difference mayindicate to the monitoring system that the solenoid-operated gas valvehas failed to function.

Referring now to FIG. 13A, voltage and current for a normally operatedmotor are shown, where the voltage trace appears sinusoidal and thecurrent trace is more jagged. In FIG. 13B, voltage and current tracesfor a compressor motor with a faulty run capacitor are shown. Visually,it is difficult to determine any difference between the time domainrepresentations in FIGS. 13A and 13B. FIG. 13C shows a time domainsubtraction of the current traces of FIGS. 13A and 13B. The differencesimply appears to be noise and in the time domain, it may be impossibleto distinguish a normally operating motor from one having a faulty runcapacitor.

Referring now to FIG. 14A, frequency domain content of the current ofthe normally operating motor of FIG. 13A is shown. Frequency bins areshown along one axis, while relative size of the frequency bin is shownon the vertical axis. Each slice 1180 may correspond to a different timewindow. In other words, FIG. 14A displays a series of FFTs performedover a number of time windows, which may be consecutive time windows.Meanwhile, FIG. 14B displays frequency domain content 1184 correspondingto the current of the faulty motor of FIG. 13B. In FIG. 14C, adifference 1188 between the frequency domain data of FIGS. 14A and 14Bis shown. When a difference at a certain frequency exceeds a threshold,faulty operation of the motor can be diagnosed. Based on which frequencybins exhibit the greatest difference, the source of the problem may besuggested. For example only, the difference spectrum 1188 may indicate afaulty run capacitor.

Referring now FIG. 15A, a data flow diagram represents the air handlermonitor module and compressor monitor module as being a triggered datalogger 1200, which supplies logged data to a cloud processor 1204.Although referred to as a cloud processor in this application, one ormore of the processes described as being performed by the cloudprocessor 1204 may instead be performed locally by the triggered datalogger 1200. For example, this processing may be performed by thetriggered data logger 1200 to reduce the amount of data that needs to beuploaded to cloud processor 1204.

The cloud processor 1204 receives the logged data and identifies keypoints in the data 1208, such as transitions between operating modes.These transitions may be identified by current spikes, such as aredepicted in FIG. 10B. Device identification 1212 specifiescharacteristics of the HVAC system being monitored, which can be used tointerpret the received data. Logger pattern forms 1216 may establishequipment specific operating characteristics from which an operationpattern 1220 is selected.

A base case pattern log 1224 may learn normal operation of the device inquestion and thereby establish a baseline. Pattern comparison 1228receives data corresponding to key points and compares that data withbase cases and selected operation patterns. Deviations by more than apredetermined amount may result in fault notification 1232. Further,anomalies that may be not be sufficient to trigger a fault may impactperformance 1236. Performance 1236 may monitor even properly runningequipment to determine if performance has degraded through normal wearand tear or through issues with the home itself, such as low insulationvalue. An information channel 1240 provides information about identifiedfaults and performance, such as alerts of decreased performance, to acontractor or homeowner, represented at 1244.

Referring now to FIG. 15B, an FFT 1260 is used to analyze HVAC operationin the frequency domain. This may allow for identification of problemsthat are difficult or impossible to reliably identify in the timedomain.

Referring now to FIG. 15C, a global knowledge base 1280 may be populatedby the monitoring company and/or installation contractors to identifyproper operation of installed systems. The global knowledge base 1280may also be updated with base cases determined by ongoing monitoring.The global knowledge base 1280 may therefore be informed by all of themonitored installation systems of a given HVAC system configuration.

Referring now to FIG. 15D, FFT processing 1300 is shown being performedlocally at the triggered data logger. The FFT 1300 may be performedlocally to reduce the amount of data uploaded to the cloud processor1204. For example only, granular time domain current data over a timewindow may be converted to frequency domain data by the FFT 1300. Thetriggered data logger 1200 may then upload only an average value of thecurrent over that time window to the cloud processor 1204, not all ofthe granular current domain data. In addition, performing the FFT 1300locally may allow for some local detection and diagnosis of faults. Thismay allow the triggered data logger 1200 to better prioritize uploadeddata, such as by immediately uploading data that appears to be relatedto an impending or present failure.

Referring now to FIG. 15E, FFT interpretation 1320 is performed in thecloud processor 1204 before being operated on by key pointidentification 1208.

Referring now to FIG. 15F, the global knowledge base 1280 of FIG. 15C iscombined with the FFT interpretation 1320 of FIG. 15E in the cloudprocessor 1204.

Referring now to FIG. 15G, another example representation of cloudprocessing is shown, where a processing module 1400 receives event datain the form of frames. The processing module 1400 uses various inputdata for detection and prediction of faults. Identified faults arepassed to an error communication system 1404. The event data 1402 may bestored upon receipt from the air handler monitor module and thecompressor monitor module.

The processing module 1400 may then perform each prediction or detectiontask with relevant data from the event data 1402. In variousimplementations, certain processing operations are common to more thanone detection or prediction operation. This data may therefore be cachedand reused. The processing module 1400 receives information aboutequipment configuration 1410, such as control signal mapping.

Rules and limits 1414 determine whether sensor values are out of bounds,which may indicate sensor failures. In addition, the rules and limits1414 may indicate that sensor values cannot be trusted when parameterssuch as current and voltage are outside of predetermined limits. Forexample only, if the AC voltage sags, such as during a brownout, datataken during that time may be discarded as unreliable.

De-bouncing and counter holds 1418 may store counts of anomalydetection. For example only, detection of a single solenoid-operated gasvalve malfunction may increment a counter, but not trigger a fault. Onlyif multiple solenoid-operated gas valve failures are detected is anerror signaled. This can eliminate false positives. For example only, asingle failure of energy consuming component may cause a correspondingcounter to be incremented by one, while detection of proper operationmay lead to the corresponding counter being decremented by one. In thisway, if faulty operation is prevalent, the counter will eventuallyincrease to a point where an error is signaled. Records and referencefiles 1422 may store frequency and time domain data establishingbaselines for detection and prediction.

A basic failure-to-function fault may be determined by comparing controlline state against operational state based on current and/or power.Basic function may be verified by temperature, and improper operationmay contribute to a counter being incremented. This analysis may rely onreturn air temperature, supply air temperature, liquid line intemperature, voltage, current, real power, control line status,compressor discharge temperature, liquid line out temperature, andambient temperature.

Sensor error faults may be detected by checking sensor values foranomalous operation, such as may occur for open-circuit or short-circuitfaults. The values for those determinations may be found in the rulesand limits 1414. This analysis may rely on return air temperature,supply air temperature, liquid line in temperature (which may correspondto a temperature of the refrigerant line in the air handler, before orafter the expansion valve), control line status, compressor dischargetemperature, liquid line out temperature, and ambient temperature.

When the HVAC system is off, sensor error faults may also be diagnosed.For example, based on control lines indicating that the HVAC system hasbeen off for an hour, processing module 1400 may check whether thecompressor discharge temperature, liquid line out temperature, andambient temperature are approximately equal. In addition, the processingmodule 1400 may also check that the return air temperature, the supplyair temperature, and the liquid line in temperature are approximatelyequal.

The processing module 1400 may compare temperature readings and voltagesagainst predetermined limits to determine voltage faults and temperaturefaults. These faults may cause the processing module 1400 to ignorevarious faults that could appear present when voltages or temperaturesare outside of the predetermined limits.

The processing module 1400 may check the status of discrete sensors todetermine whether specifically-detected fault conditions are present.For example only, the status of condensate, float switch, and floorsensor water sensors are checked. The water sensors may be cross-checkedagainst operating states of the HVAC system. For example only, if theair conditioning system is not running, it would not be expected thatthe condensate tray would be filling with water. This may insteadindicate that one of the water sensors is malfunctioning. Such adetermination could initiate a service call to fix the sensor so that itcan properly identify when an actual water problem is present.

The processing module 1400 may determine whether the proper sequence offurnace initiation is occurring. This may rely on event and dailyaccumulation files 1426. The processing module 1400 may perform statesequence decoding, such as by looking at transitions as shown in FIG.10B and expected times during which those transitions are expected.Detected furnace sequences are compared against a reference case anderrors are generated based on exceptions. The furnace sequence may beverified with temperature readings, such as observing whether, while theburner is on, the supply air temperature is increasing with respect tothe return air temperature. The processing module 1400 may also use FFTprocessing to determine that the sparker or igniter operation andsolenoid-operated gas valve operation are adequate.

The processing module 1400 may determine whether a flame probe or flamesensor is accurately detecting flame. State sequence decoding may befollowed by determining whether a series of furnace initiations areperformed. If so, this may indicate that the flame probe is notdetecting flame and the burner is therefore being shut off. Thefrequency of retries may increase over time when the flame probe is notoperating correctly.

The processing module 1400 may evaluate heat pump performance bycomparing thermal performance against power consumption and unithistory. This may rely on equipment configuration data 1410, includingcompressor maps when available.

The processing module 1400 may determine refrigerant level of the airconditioning system. For example, the processing module 1400 may analyzethe frequency content of the compressor current and extract frequenciesat the third, fifth, and seventh harmonics of the power linefrequencies. This data may be compared, based on ambient temperature, tohistorical data from when the air conditioning system was known to befully charged. Generally, as charge is lost, the surge frequency maydecrease. Additional data may be used for reinforcement of a lowrefrigerant level determination, such as supply air temperature, returnair temperature, liquid line in temperature, voltage, real power,control line status, compressor discharge temperature, and liquid lineout temperature.

The processing module 1400 may alternatively determine a low refrigerantcharge by monitoring deactivation of the compressor motor by a protectorswitch, may indicate a low refrigerant charge condition. To preventfalse positives, the processing module 1400 may ignore compressor motordeactivation that happens sooner than a predetermined delay after thecompressor motor is started, as this may instead indicate anotherproblem, such as a stuck rotor.

The processing module 1400 may determine the performance of a capacitorin the air handler unit, such as a run capacitor for the circulatorblower. Based on return air temperature, supply air temperature,voltage, current, real power, control line status, and FFT data, theprocessing module 1400 determines the time and magnitude of the startcurrent and checks the start current curve against a reference. Inaddition, steady state current may be compared over time to see whetheran increase results in a corresponding increase in the differencebetween the return air temperature and the supply air temperature.

Similarly, the processing module 1400 determines whether the capacitorin the compressor/condenser unit is functioning properly. Based oncompressor discharge temperature, liquid line out temperature, ambienttemperature, voltage, current, real power, control line status, and FFTcurrent data, control determines a time and magnitude of start current.This start current is checked against a reference in the time and/orfrequency domains. The processing module 1400 may compensate for changesin ambient temperature and in liquid line in temperature. The processingmodule 1400 may also verify that increases in steady state currentresult in a corresponding increase in the difference between thecompressor discharge temperature and the liquid line in temperature.

The processing module may calculate and accumulate energy consumptiondata over time. The processing module may also store temperatures on aperiodic basis and at the end of heat and cool cycles. In addition, theprocessing module 1400 may record lengths of run times. An accumulationof run times may be used in determining the age of wear items, which maybenefit from servicing, such as oiling, or preemptive replacing.

The processing module 1400 may also grade the homeowner's equipment. Theprocessing module 1400 compares heat flux generated by the HVACequipment against energy consumption. The heat flux may be indicated byreturn air temperature and/or indoor temperature, such as from athermostat. The processing module 1400 may calculate the envelope of theresidence to determine the net flux. The processing module 1400 maycompare the equipment's performance, when adjusted for residenceenvelope, against other similar systems. Significant deviations maycause an error to be indicated.

The processing module 1400 uses a change in current or power and thetype of circulator blower motor to determine the change in load. Thischange in load can be used to determine whether the filter is dirty. Theprocessing module 1400 may also use power factor, which may becalculated based on the difference in phase between voltage and current.Temperatures may be used to verify reduced flow and eliminate otherpotential reasons for observed current or power changes in thecirculator blower motor. The processing module 1400 may also determinewhen an evaporator coil is closed. The processing module 1400 uses acombination of loading and thermal data to identify the signature of acoil that is freezing or frozen. This can be performed even when thereis no direct temperature measurement of the coil itself.

FFT analysis may show altered compressor load from high liquid fraction.Often, a frozen coil is caused by a fan failure, but the fan failureitself may be detected separately. The processing module 1400 may usereturn air temperature, supply air temperature, liquid line intemperature, voltage, current, real power, and FFT data from both theair handler unit and the compressor condenser unit. In addition, theprocessing module 1400 may monitor control line status, switch statuses,compressor discharge temperature, liquid line out temperature, andambient temperature. When a change in loading occurs that might beindicative of a clogged filter, but the change happened suddenly, adifferent cause may be to blame.

The processing module 1400 identifies a condenser blockage by examiningthe approach temperature, which is the difference between the liquidline out temperature and the ambient temperature. When the refrigeranthas not been sufficiently cooled from the condenser dischargetemperature (the input to the condenser) to the liquid line outtemperature (output of the condenser), adjusted based on ambienttemperature, the condenser may be blocked. Other data can be used toexclude other possible causes of this problem. The other data mayinclude supply air temperature, return air temperature, voltage,current, real power, FFT data, and control line status both of the airhandler unit and the compressor condenser unit.

The processing module 1400 determines whether the installed equipment isoversized for the residence. Based on event and daily accumulationfiles, the processing module evaluates temperature slopes at the end ofthe heating and/or cooling run. Using run time, duty cycle, temperatureslopes, ambient temperature, and equipment heat flux versus home flux,appropriateness of equipment sizing can be determined. When equipment isoversized, there are comfort implications. For example, in airconditioning, short runs do not circulate air sufficiently, so moistureis not pulled out of the air. Further, the air conditioning system maynever reach peak operating efficiency during a short cycle.

The processing module 1400 evaluates igniter positive temperaturecoefficient based on voltage, current, real power, control line status,and FFT data from the air handler unit. The processing module comparescurrent level and slope during warm-up to look for increased resistance.Additionally, the processing module may use FFT data on warm-up todetect changes in the curve shape and internal arcing.

The processing module also evaluates igniter negative temperaturecoefficient based on voltage, current, real power, control line status,and FFT data from the air handler unit. The processing module 1400compares current level and slope during warm-up to look for increasedresistance. The processing module 1400 checks initial warm-up and troughcurrents. In addition, the processing module 1400 may use FFT datacorresponding to warm-up to detect changes in the curve shape andinternal arcing.

The processing module 1400 can also evaluate the positive temperaturecoefficient of a nitride igniter based on voltage, current, real power,control line status, and FFT data from the air handler unit. Theprocessing module 1400 compares voltage level and current slope duringwarm-up to look for increased resistance. In addition, the processingmodule 1400 uses FFT data corresponding to warm-up to detect changes inthe curve shape, drive voltage pattern, and internal arcing. Changes indrive voltage may indicate igniter aging, so those adjustments should bedistinguished from changes to compensate for gas content and otherfurnace components.

Referring now to FIG. 16A, a table depicts example faults and features,with respect to the air handler unit, that can be detected and/orpredicted. Each row corresponds to a fault or feature that may bedetected or predicted, and an asterisk is located in each column used tomake the detection or prediction. For both detection and prediction,some data may be used as the primary data for making the determination,while other data is used for compensation. Temperatures and voltages areused to perform compensation for those rows having an asterisk in thecorresponding column.

The primary columns include timing of when events are detected, timedomain current information, temperatures (including residencetemperature as measured by the thermostat), pressures (such asrefrigerant system pressures and/or air pressures), FFT data, and directdetection. Direct detection may occur when a status or control linedirectly indicates the fault or feature, such as when a water sensorindicates an overfull condensate tray.

Referring now to FIG. 16B, a table depicts example faults and features,with respect to the compressor/condenser unit, that can be detectedand/or predicted. In FIG. 16B, outside ambient temperature and voltagesmay be used to compensate primary data.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. For purposes of clarity, thesame reference numbers will be used in the drawings to identify similarelements. As used herein, the phrase at least one of A, B, and C shouldbe construed to mean a logical (A or B or C), using a non-exclusivelogical OR. It should be understood that one or more steps within amethod may be executed in different order (or concurrently) withoutaltering the principles of the present disclosure.

As used herein, the term module may refer to, be part of, or include anApplication Specific Integrated Circuit (ASIC); an electronic circuit; acombinational logic circuit; a field programmable gate array (FPGA); aprocessor (shared, dedicated, or group) that executes code; othersuitable hardware components that provide the described functionality;or a combination of some or all of the above, such as in asystem-on-chip. The term module may include memory (shared, dedicated,or group) that stores code executed by the processor. For example only,the processor may be a 16-bit PIC24 MCU microprocessor manufactured byMichrochip Technology, Inc.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes,and/or objects. The term shared, as used above, means that some or allcode from multiple modules may be executed using a single (shared)processor. In addition, some or all code from multiple modules may bestored by a single (shared) memory. The term group, as used above, meansthat some or all code from a single module may be executed using a groupof processors. In addition, some or all code from a single module may bestored using a group of memories.

The apparatuses and methods described herein may be implemented by oneor more computer programs executed by one or more processors. Thecomputer programs include processor-executable instructions that arestored on a non-transitory tangible computer readable medium. Thecomputer programs may also include stored data. Non-limiting examples ofthe non-transitory tangible computer readable medium are nonvolatilememory, magnetic storage, and optical storage.

1. A monitoring system for a heating, ventilation, and air conditioning(HVAC) system of a residence, the monitoring system comprising: amonitoring device installed at the residence, wherein the monitoringdevice (i) measures an aggregate current supplied to a plurality ofcomponents of the HVAC system and (ii) transmits current data based onthe measured aggregate current; and a server, located remotely from theresidence, that receives the transmitted current data and, based on thereceived current, assesses whether a failure has occurred in a firstcomponent of the plurality of components of the HVAC system and assesseswhether a failure has occurred in a second component of the plurality ofcomponents of the HVAC system.
 2. The monitoring system of claim 1wherein the monitoring device samples the aggregate current over a timeperiod, performs a frequency domain analysis on the samples over thetime period, and transmits frequency domain data to the server.
 3. Themonitoring system of claim 2 wherein the server identifies transitionpoints in the current data and analyzes the frequency domain data aroundthe identified transition points.
 4. The monitoring system of claim 2wherein the server determines whether the failure has occurred in thefirst component by comparing the frequency domain data to baseline data.5. The monitoring system of claim 4 wherein the server adapts thebaseline data based on normal operation of the HVAC system.
 6. Themonitoring system of claim 2 wherein the monitoring device determines asingle current value for the time period and transmits the singlecurrent value to the server without transmitting the samples to theserver.
 7. The monitoring system of claim 6 wherein the single currentvalue is one of a root mean squared current, an average current, and apeak current.
 8. The monitoring system of claim 1 wherein the monitoringdevice measures the aggregate current over a series of consecutive timeperiods and transmits a frame of information to the server for each ofthe time periods.
 9. The monitoring system of claim 8 wherein, for afirst period of the time periods, the monitoring device transmits afirst frame including (i) a single value of the aggregate current duringthe first period and (ii) a frequency domain representation of theaggregate current during the first period.
 10. The monitoring system ofclaim 9 wherein the first frame does not include individual samples ofthe aggregate current.
 11. The monitoring system of claim 9 wherein thefirst frame includes a voltage measurement of power arriving at the HVACsystem, a temperature measurement, and a representation of status ofHVAC control lines during the first period.
 12. The monitoring system ofclaim 1 wherein the monitoring device records control signals from athermostat and transmits information based on the control signals to theserver.
 13. The monitoring system of claim 12 wherein the controlsignals include at least one of call for heat, call for fan, and callfor cool.
 14. The monitoring system of claim 1 wherein the monitoringdevice is located in close proximity to an air handler unit of the HVACsystem.
 15. The monitoring system of claim 14 further comprising asecond monitoring device located in close proximity to a secondenclosure of the HVAC system, wherein the second enclosure includes atleast one of a compressor and a heat pump heat exchanger.
 16. Themonitoring system of claim 15 wherein the second monitoring device (i)measures an aggregate current supplied to a plurality of components ofthe second enclosure and (ii) transmits current data based on themeasured aggregate current to the server.
 17. The monitoring system ofclaim 16 wherein the second monitoring device transmits the current datato the server via the monitoring device.
 18. The monitoring system ofclaim 1 wherein the monitoring device includes a switch that selectivelyinterrupts an enabling signal to a compressor of the HVAC system. 19.The monitoring system of claim 18 wherein the monitoring deviceinterrupts the enabling signal in response to at least one of (i) avalue from a water sensor, (ii) a locked rotor condition of thecompressor, and (iii) a command from the server.
 20. The monitoringsystem of claim 1 wherein the server (i) generates an alert in responseto determining presence of a fault of either the first component or thesecond component and (ii) sends the alert to at least one of a homeownerof the residence and an installation contractor.
 21. The monitoringsystem of claim 1 wherein the server (i) selectively predicts animpeding failure of the first component based on the received currentdata, (ii) selectively predicts an impeding failure of the secondcomponent based on the received current data, and (iii) generates analert in response to prediction of impending failure.
 22. The monitoringsystem of claim 1 wherein the plurality of components of the HVAC systemincludes at least two components selected from: a flame sensor, asolenoid-operated gas valve, a hot surface igniter, a circulator blowermotor, an inducer blower motor, a compressor, a pressure switch, acapacitor, an air filter, a condensing coil, an evaporating coil, and acontactor.